A boy weighing 50 kg finished long jump at a distance of 8 m . Considering that he moved along a parabolic…

A boy weighing 50 kg finished long jump at a distance of 8 m . Considering that he moved along a parabolic path and his angle of jump is $45^{\circ}$, his initial $K E$ is
  1. 960 J
  2. 1560 J
  3. 2460 J
  4. 1960 J

Solution

$\mathrm{R}=8 \mathrm{~m}, \theta=45^{\circ}$ $\begin{aligned} & \therefore \quad R=\frac{u^2 \sin 2 \theta}{g}=\frac{u^2 \sin 90^{\circ}}{g}=\frac{u^2}{9.8} \\ & \therefore \quad u^2=9.8 R=9.8 \times 8=78.4 \end{aligned}$ $\therefore \quad$ Initial K.E. of the man, $(\mathrm{K} . \mathrm{E})_2=\frac{1}{2} \mathrm{mu}^2=\frac{1}{2} \times 50 \times 78.4=1960 \mathrm{~J}$

Asked in: AP EAMCET 2024 (22 May Shift 1)

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